Colour: An Elementary Manual for Students

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Cassell, 1891 - Color - 192 pages
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Page 4 - This reflection of light in a countless number of different directions by the small fibres which compose the paper is the real cause both of the whiteness and opacity of papers. The greater these countless reflections the greater the opacity— the less the transparency. " The numerous small reflections which occur from and between the surfaces of the felted fibres in a piece of white paper may be greatly lessened by wetting or oiling the paper, when it becomes less opaque, and at the same time greyer...
Page 33 - This bending of the waves of light has been termed diffraction. The source of light in studying the phenomena of diffraction should be a luminous or highly illuminated point. A silvered bead, or steel globule, or the focus of rays obtained by the action of a lens on a beam...
Page 8 - Bodies are said to be transparent when they permit light to pass so freely as to allow objects to be perfectly discerned through them.
Page 5 - ... bodies by the aid of the light which they reflect irregularly, or scatter ; a perfectly regular reflection gives, on the contrary, an image of the source of light, not of the object illuminated. It is only light which is regularly reflected which can be shown to obey the great law of reflection, which is this :— " The angle which an incident ray of light makes with a perpendicular to the reflecting surface, is equal to the angle which the reflected ray makes with that perpendicular ;" in other...
Page 13 - ... the beam besides its permanent refraction. If the light be simple, if its wave-lengths be of one measure only, it will be simply deflected ; but if, as is nearly always the case, the light be compound — if its waves are of different lengths — then the prism will differently affect them. It...
Page 36 - ... half wave-lengths. Then it will be found that the bubble is black, because the two reflected beams are in complete discordance ; and a destruction of light follows. Then, again, soap-bubbles may vary very much in the thickness of different parts. As the waves of light differ in length, so they will require different thicknesses to produce accordance and discordance. The result of this is that a thickness of film which is competent to extinguish one colour will not extinguish other > colours....
Page 4 - ... surface is irregular, and that from a coloured surface coloured. A polished plane metallic surface affords an example of the first kind of reflection, a piece of chalk of the second. So great is the difference in effect produced by regular reflection from that produced by irregular reflection, that if an illuminated polished body could be found which was wholly incapable of irregularly reflecting any part of the light falling upon it, that body would be invisible. We may, therefore, say that...
Page 53 - Rood, for a prismatic spectrum divided into 1,000 parts between the fixed lines A and H. Rood, moreover, has named the several coloured regions, so that with these two data (of spaces and luminosities) he has been able to construct the following Table showing the Amounts of Coloured Light in 1,000 Parts of White Sunlight.
Page 11 - ... till they reach the eye. In passing from air into water or glass the refracted ray is bent towards the perpendicular ; in passing out of water or glass into air the reverse refraction occurs, and to a precisely equivalent extent. If, therefore, a beam of light enters obliquely a piece of glass, the faces of which are parallel, the refraction towards the perpendicular on entering the glass will be exactly compensated by the refraction from the perpendicular on leaving the lower surface, and so...
Page 5 - Another law here to be mentioned is, that both the incident and the reflected rays of light are in the same plane, which is perpendicular to the reflecting surface. We shall have to refer to these laws of reflection, to reflection at varying angles and from different substances, and to the different kinds of reflection enumerated above, when we proceed to discuss the subject of Colour. A few words may now be said on luminous bodies, or those which emit light.

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